1. Technical Field
The present invention generally relates to phased array systems and more particularly to integrated phased-array transceivers operating at millimeter-wave frequencies
2. Description of the Related Art
Phased array transceivers are a class of multiple antenna systems that achieve spatial selectivity through control of the time delay difference between successive antenna signal paths. A change in this delay difference modifies the direction in which the transmitted/received signals add coherently, thus “steering” the electromagnetic beam using the interference of multiple waves.
The 57- to 66-GHz band supports extremely high-rate (1-10 Gb/s) wireless digital communication. However, fixed-antenna 60-GHz systems are sensitive to obstructions in the line of sight (LOS). As such, beam-steering technologies are especially useful for communications in this range.
There are several prominent commercial applications of phased arrays at millimeter-wave frequencies. The 7 GHz Industrial, Scientific and Medical (ISM) band at 60 GHz is currently being widely investigated for indoor, multi-gigabit per second Wireless Personal Area Networks (WPANs). In such an application, the line-of-sight link between the transmitter and receiver can easily be broken due to obstacles in the path. Phased arrays can harness reflections of the walls due to their beam-steering capability, thus allowing the link to be restored.
Phased array systems use a plurality of signal paths, each having a variable time delay. The variable time delay in each signal path in the receiver produce a propagation delay in each signal as they reach their successive antennas. In this way, with appropriate delays at each element, the combined output signal will have a larger amplitude in a desired direction than could be obtained with a single element.